Life-cycle cost analysis of building wall and insulation materials

Heat transfer through building opaque envelope is responsible for approximately half of the total heat loss and gain to and from the surroundings. Therefore, insulation materials are commonly used in the building envelope to reduce the heat transfer. Recently, lightweight wall materials with lower thermal conductivity are used in construction along with the commonly used materials such as heavy concrete and earthen materials. In this perspective, there is a need to understand the optimum insulation thickness for different types of building construction materials to minimize unnecessary usage of insulation materials. This study investigated the optimum insulation thickness for different construction materials following a life-cycle approach, where an analytical optimization methodology based on the degree-days method and life-cycle cost analysis was used. In total, 4 insulation materials and 15 building construction materials were considered in the optimization study. The objective function was to minimize life-cycle cost corresponding to the decision variables including insulation thickness and the thermal conductivity of insulation and wall materials. The results showed that the use of insulation in lightweight wall materials is not economically feasible because of their negligible cost-saving potential (below US$2.5/m(2)-year). However, the walls with heavy concrete and earthen materials that have high thermal mass must be insulated due to their highest cost-saving potential (US$14-26.39/m(2)-year).